1. Field of the Invention
This invention relates to age hardenable iron-base alloy weld deposits. More particularly the invention relates to such deposits which provide superior galling resistance and hot hardness up to at least 1450.degree. F. (790.degree. C.). Our weld deposits are preferably applied to ferrous alloy base materials such as low alloy, carbon, mild and tool steels.
2. Description of the Prior Art
Many industrial applications involve metal-to-metal wear at high temperatures; examples of such applications are hot extrusion dies and hot shearing blades which may reach temperatures as high as 1450.degree. F. (790.degree. C.) in service. Alloys used in such applications, either as the working parts or as surface layers on the working parts, should have good galling resistance and good hardness at working temperatures.
Heretofore, the most widely used alloys for applications such as those described above have been expensive nickel-base and cobalt-base alloys, the former typified by the wrought alloy INCONEL* 718 and the latter by commercial welding alloys classified by the American Welding Society (AWS) as ER CoCr-A and ER CoCr-C, which are applied as weld deposits on various base materials. More recently, alloys known as TRIBALOY 400** (cobalt base) and TRIBALOY 700** (nickel base) have been introduced; in the heat treated condition these alloys contain large volume percentages of Laves phase intermetalic constituents. The TRIBALOYS are generally applied as powders to a base structure and then fused by the heat of an electric arc, although in experimental work they have been deposited using shielded metal arc welding electrodes. FNT *Registered trademark of the International Nickel Co. FNT **Trademark of the E. I. DuPont deNemours Co.
The nickel and cobalt base alloys of the prior art, particularly the TRIBALOYS which contain high percentages of molybdenum, are characterized by extremely high cost, and therefore their use has been limited. Moreover, several of the nickel and cobalt base alloys of the prior art are prone to crack when applied as weld deposits, and this further limits their utility. Finally, the TRIBALOY type alloys require a rather long aging treatment in order to develop optimum properties, which adds to their cost.
Another alloy suggested for possible use in high temperature metal-to-metal wear applications is a chromium-and cobalt-containing tool steel disclosed in U.S. Pat. No. 3,508,912. However, this alloy is not balanced for use as a weld deposit; i.e. the patent disclosure does not teach weld metal composition necessary to obtain optimum hot hardness properties while avoiding excessive cracking. Consequently, the alloy disclosed in the patent, while useful to some extent as a wrought product, has serious disadvantages when applied as a weld deposit.